Can milk be harmful after a certain age?

Q: Is drinking of milk harmful after a certain age?

A:Mothers milk is the best food for a baby (and might even be good for adults, although this obviously is not a practical consideration!), and cows milk is a good substitute and is suitable for adults of all ages. The milk of other animals such as the yak is also a good food, and is a main staple of many peoples throughout life. Unfortunately many adults gradually lose the necessary digestive enzymes from their gastrointestinal tract, and they become intolerant of milk. However, if it can be tolerated then milk is a very good food from infancy through old age. One comment: producing milk is not always an economic use of resources, such as feeding crops, and cattle rearing has adverse environmental impacts.